Method for the manufacture of antibacterial viscose filament rayon and a product obtained using that method

ABSTRACT

The antibacterial viscose rayon, according to the invention, is used for the manufacture of any type of textile articles, including items intended for medical use, ensuring a more lasting antibacterial and antifungal protection due to the uniform distribution of the antibacterial additive throughout the entire volume of the fibre. According to the invention, immediately before spinning, the viscose is mixed and homogenized with an antibacterial additive, and then spun following the classical procedure: the viscose solution, with required and strictly specified parameters is fed under pressure to the spinnerets of the spinning machine from which the cellulose solution enters a spin bath, where as a result of the chemical reactions in course is transformed into fibres subjected afterwards to a subsequent treatment. According to the invention, in the production of dope dyed antibacterial rayon, into the preliminarily prepared suspension composed of one or a couple of pigments, a specified amount of antibacterial additive is introduced, the obtained mix is homogenized and filtered, and then subjected to the classical stages of spinning and subsequent treatments.

SCOPE OF APPLICATION

The present invention concerns a method for the manufacture ofantibacterial viscose filament rayon and a product obtained using thatmethod.

PREVIOUS STATE OF THE TECHNOLOGY

The classical technology for production of viscose rayon has notdeveloped much notwithstanding the long time passed since its creation,as the process itself is very conservative and strongly affected byvarious external and other factors. In general terms, this classicalprocess of spinning performed by different types of spinning machinesconsists in the following:

Firstly, the cellulose undergoes the so-called mercerization, beingprocessing of the initial pulp with a concentrated solution of sodiumhydroxide (NaOH), resulting in alkali cellulose, which afterwards issubjected to destruction, i.e. aging, where the degree of polymerizationis decreased. This is followed by temperature reduction and dosing ofthe alkali cellulose amount for the production of one batch of viscose.The next stage is carbon-disulphide treatment which causes the alkalicellulose to transform into cellulose xanthate, whose most importantproperty is that it is soluble in diluted solutions of sodium hydroxide.The cellulose solution of one batch is mixed and homogenized with theone from the previous and the following batch, deaerated, and filteredto remove the impurities. Then the already cleared viscose solution,with required and strictly specified parameters, is fed under pressureto the spinning machines. Wet spinning is performed by passing thecellulose solution, by means of a dosing pump, through the spinneretholes into the spin bath, where as a result of the chemical reactionsthe cellulose from the cellulose solution transforms into fibers.

This is followed by washing procedures where the freshly-spun sour rayonis treated with various solutions to clear the residues of the spinbath, the sodium sulfate and sulfur resulted from the chemical reactionsduring spinning.

The washed semi-finished product is then dried, conditioned, rewound andsent for quality control inspection and packaging as a finished product.

In the production of dope dyed viscose rayon to the viscose solution,prepared for spinning, a preliminarily prepared pigment suspension madeof one or a couple of pigments is added. The required quantity of thesuspension is dosed into and mixed to homogenization with the viscose,in order the pigment particles to be distributed uniformly through thewhole volume of this solution. To the dyed and homogenized solution ofthe cellulose are further applied the classical stages of spinning,washing, drying, conditioning, rewinding and sent for quality controlinspection and packaging as a finished product.

Due to specific needs of the textile industry, textiles with newconsumer qualities are required, for example such with a specific degreeof antibacterial and antifungal protection. They are obtained by meansof an antibacterial additive, which is usually a solution or suspensionof the antibacterial substance(s) in water in the presence of specificamounts of equalizers, dispersing agents, wetting agents, softeners, andetc.

In order to obtain antibacterial or antifungal protection, the followingtypes of treatment are known from the established practice:

Textile application by pad—usually carried out on Foulard through anaqueous pad bath. The bath in these cases should be perfectly preparedimmediately prior to use, strictly observing the obligatory requirementfor continuous stirring in order to maintain a constant degree ofdispersion of the dispersion system, in case the antibacterial additiveis in the form of dispersion. The usual concentration of the additiveused is 0.14 to 0.70% of the fabric weight to be treated, as thetreatment itself can be performed by adding to the bath not only theantibacterial additive, but also the rest of the finishing preparations.In such cases though, it is required that preliminary tests be run fordetermining the compliance of the antibacterial additive with the othersubstances. The fabric with the antibacterial additive applied isimmediately dried and thus the antibacterial additive remains more orless fixed on its surface, i.e. it doesn't reach the cross section ofthe various fibres used for the manufacture of the fabric. How long theantibacterial effect will last can be determined after performing acouple of washing cycles assessing after each of them the degree ofchange of the antibacterial protection.

Textile application through exhaust—can be applied to fabrics,especially the ones made only from synthetic fibers. This method alsouses a bath in proportion 10:1 or less, at pH 4-8 and exhaust time of atleast 30 min. at a temperature of at least 80° C. The use of lowertemperatures can significantly reduce the exhaust efficiency. In thismethod the application of the antibacterial additive is also only on thesurface of the woven or knitted fabric. The additional use of equalizerscan contribute to the uniform distribution of the antibacterial additiveacross the entire surface treated.

The main disadvantages of these methods of antibacterial additiveapplication is that the duration of the effect of the antibacterialadditive depends solely on the stability of its fixing to the treatedsurface, as no uniformity of the antibacterial protection can beguaranteed.

Besides, the antibacterial additive is absorbed partially, i.e. a bigportion of it remains in the bath after treatment, as the same is thendischarged into the waste water. Therefore, the use of these methodsmeans higher expenses for waste water cleansing, as well as ecologicalproblems.

There is a method for obtaining antibacterial rayon with antifungal andantiseptic properties and light fastness, described in JPH09310235/A/.According to the method, from 5 to 10% composition of inorganiccompounds with particle size less than 5 micron is blended with theviscose in a mixer, or in the tank before its deaeration at the stage ofhomogenization of the separate batches of viscose, or in the viscosetank before its deaeration. The obtained mix after all the successivestages of filtration is passed to the spinning department for spinning.The ceramic composition of inorganic compounds is obtained byhomogenizing 20-80% serpentine particles/base material/ with 20-80%silica particles and 10-40% of zinc oxide particles followed by asubsequent sintering of the mix.

The disadvantage of this method is the complication of the otherprocesses of viscose preparation—filtering, ripening and evenspinning—due to the high concentration of inorganic particles in theviscose composition introduced too early—at the stage of mixing of theviscose solution with the antibacterial ceramic composition.

Furthermore, the early introduction of the antibacterial ceramicadditive requires separate flows of movement of the untreated and themixed with the antibacterial component viscose to the spinning machines,i.e. they require separate flow-lines, if both types of rayon areproduced simultaneously.

There is a method for obtaining fibres with antibacterial properties,described in patent application JPH17173711/A/ for obtaining fibres withhaving antibacterial capability, retaining its antibacterial capabilityeven after washed repeatedly, thus useful for sheets and white overallsby imparting in a specific mode viscose rayon with an anion-carryinghigh molecular substance and a quaternary ammonium salt compound. Ananion-carrying high molecular substance is homogeneously dispersed at0.01-30% in the viscose rayon and a quaternary ammonium salt compound ofthe formula R1 is a 8-30C saturated or unsaturated fatty acid residue,formula R2 is a 8-30C saturated or unsaturated fatty acid residue orCH3, didccil dimethyl ammonium chloride is held at 0.001-10 wt % on thesurface of the viscose rayon. The fibres obtained by means of thismethod have the flaws as mentioned above, owing to the surface treatmentitself of the already manufactured rayon.

There is a method for the manufacture of fibres with antisepticproperties described in patent application No. CN1779004/A/. Theantiseptic additive used is silver mixed with a cellulose sulfonic acidester. The quantity of the silver is from 0.5% to 5.0% in relation tothe weight of the cellulose. This method though is unacceptable forobtaining viscose fibres or rayon, as the silver from the additivereacts with the released during the spinning hydrogen sulphide to silversulphide, which gives the product a grey shade.

The purpose of the invention is to be suggested a manufacture method forraw bright white and coloured viscose rayon with the aforementionedantibacterial and antifungal properties.

The method developed in accordance with the invention is based onexisting classical process of spinning with the addition of more stages,in order to obtain a fibre in which the antibacterial additive isdistributed uniformly through the entire volume and cross-section of therayon. Thus a much more lasting antibacterial and antifungal protectionis achieved, without pollution of the waste water.

NATURE OF THE INVENTION

According to the invention, a direct method for direct viscose rayonproduction with antibacterial properties is suggested, which consists ofthe following stages:

Firstly, the cellulose undergoes the so-called mercerization, beingprocessing of the initial pulp with a concentrated solution of sodiumhydroxide (NaOH), resulting in alkali cellulose, which afterwards issubjected to destruction, i.e. aging, where the degree of polymerizationis decreased. This is followed by temperature reduction and dosing ofthe alkali cellulose amount for the production of one batch of viscose.The next stage is carbon-disulphide treatment which causes the alkalicellulose to transform into cellulose xanthate, whose most importantproperty is that it is soluble in diluted solutions of sodium hydroxide.The cellulose solution of one batch is mixed and homogenized with theone from the previous and the following batch, deaerated, and filteredto remove the impurities. Then the already cleaned viscose solution,with strictly specified parameters, is fed under pressure to therespective number of spinning machines.

According to the invention immediately before spinning, the viscose ismixed with an antibacterial additive, homogenized and spun directlyfollowing the classical procedure, that is, the already cleared viscosesolution, with strictly specified parameters, is fed under pressure tothe spinning machines. Wet spinning is performed by passing thecellulose solution, by means of a dosing pump, through the spinneretholes into the spin bath, where as a result of the chemical reactionsthe cellulose from the cellulose solution transforms into fibers.

This is followed by washing procedures where the freshly-spun sour rayonis treated with various solutions to clear the residues of the spinbath, the sodium sulfate and sulfur resulted from the chemical reactionsduring spinning. The washed semi-finished product is then dried,conditioned, rewound and sent for quality control inspection andpackaging as a finished product.

According to the invention, in the production of dope dyed viscose rayonto the preliminarily prepared pigment suspension, made of one or acouple of pigments, a specified amount of antibacterial additive isadded. Then the required quantity of pigment and antibacterial additivemixed suspension is dosed into and mixed to homogenization with theviscose, in order the pigment particles and the antibacterial additiveto be distributed uniformly through the whole volume of the alreadycoloured solution. Wet spinning is performed by passing the alreadycoloured and antibacterial-treated cellulose solution, by means of adosing pump, through the spinneret holes into the spin bath, where as aresult of the chemical reactions the cellulose from the cellulosesolution transforms into fibers.

This is followed by washing procedures where the freshly-spun sour rayonis treated with various solutions to clear the residues of the spinbath, the sodium sulfate and sulfur resulted from the chemical reactionsduring spinning.

The washed semi-finished product is then dried, conditioned, rewound andsent for quality control inspection and packaging as a finished product.

According to the invention, the amount of the antibacterial additive isfrom 0.01 to 5% in relation to the cellulose quantity in the viscosesolution, as in the case of utilization of the additive KW 48 thisconcentration is from 0.5 to 3.5%.

In addition, according to the invention, the preparation of theantibacterial suspension and its storage are at temperatures rangingfrom +20° C. to −4° C.

Furthermore, according to the invention the antibacterial suspension isfiltered for removal of all particles exceeding the size of 5 microns.

During the performance of the invention, viscose rayon withantibacterial properties is obtained, which can be used for theproduction of any type of items, including products intended for medicaluse, as the antibacterial additive is distributed uniformly throughoutthe entire volume and cross-section of the rayon fibre, which suggests asignificantly longer effect, and respectively more lasting antibacterialand antifungal protection.

Besides, the antibacterial additive is 100% utilized and there are noresidual and polluting the waste water quantities, which is extremelyimportant from environmental point of view.

In addition to all other advantages, the change of the stage where theantibacterial additive is used gives the possibility for the productionof coloured antibacterial viscose rayon by preparing combined recipesfor the production of colours, as the antibacterial additive becomes anintegral component of the dyeing recipe. The combined pigment andantibacterial suspension is transported to a homogenizing tank and laterinto the cellulose solution following the innovative mode, and then itis directly subjected to spinning.

SHORT DESCRIPTION OF THE FIGURES ENCLOSED

FIG. 1 illustrates the sequence of the processes of the manufacture ofviscose rayon filament according classical technology of manufacturing

FIG. 2 presents dope dyed viscose rayon filament production (10-1) withand without the use of antibacterial additive.

FIG. 3 presents a detailed construction of an original centrifugalspinning machine.

In FIG. 4 a chart presents the recipe for the preparation of thesuspension with antibacterial additive, introduced in the cellulosesolution in the homogenizer.

In FIGS. 5a and 5b are given the results of external laboratoryinvestigations of antibacterial rayon, manufactured using the methodaccording to the invention.

MODEL PERFORMANCE OF THE METHOD FOR PRODUCTION OF ANTIBACTERIAL VISCOSERAYON

With reference to FIGS. 1, 2 and 3 a model performance of the methodaccording to the invention is demonstrated.

Firstly, the base cellulose is fed into unit 1 formercerization—treatment of the initial pulp with a concentrated solutionof sodium hydroxide (NaOH), resulting in alkali cellulose, whichafterwards in unit 2 is subjected to destruction, i.e. aging, where thedegree of polymerization is decreased. In unit 3 temperature reductiontakes place, and in unit 4—dosing of the alkali cellulose amount for theproduction of one batch of viscose. In unit 5 is introduced the nextstage—carbon disulphide treatment of the alkali cellulose untilobtaining cellulose xanthate, whose most important property is that itis soluble in sodium hydroxide diluted solutions. In units 6 and 7 thesolution of cellulose from one batch is mixed and homogenized with theone from the previous and the following batch, deaerated, and thenfiltered in unit 8 for removal of the impurities.

Then, in case that there is no production of coloured rayon, the viscosesolution with requires and strictly defined parameters is fed underpressure to the spinning machines 10 in a pipe collector 38 which ispermanently full of cellulose solution under pressure for the preventionof incidence of a gas phase. This collector 38 provides the necessaryquantity of cellulose solution to the spinneret for each workingposition of the rayon spinning machine 10 through the respective dosingpump 22 (FIG. 3). Passed through the spinneret 26 (FIG. 3), thecellulose gets into a spin bath 11 where, as a result of the chemicalreactions in course, the cellulose from the cellulose solution istransformed into rayon fibres. Leaving the bath the freshly-spun sourrayon is transported to the centrifuge 29 (FIG. 3). When it is filled upto a specific volume, the fibre between spinning devices 27 and 28 (FIG.3) is interrupted manually and wound on spinning device 27 only. Duringthat period the centrifuge 29 is stopped, the formed in it rayon cake istaken out and the centrifuge is again put into operation. When the sameenters in operating mode, the rayon fibre from spinning device 27 isagain transferred to spinning device 28 from where it is led to thecentrifuge 29, giving start to the production of the next rayon cake.

Then this is followed by washing procedures in unit 12, where thefreshly-spun sour rayon is treated with different solutions, prepared inunit 13, for removal of residues from the spin bath, the sodium sulfateand basic sulfur resulted from the chemical reactions during spinning.

The obtained semi-finished product is then dried, conditioned, rewoundand sent for quality control inspection and packaging as a finishedproduct—units 14, 15, 16, 17, 18 and after quality control inspection itis stored in unit 19.

In the production of dope dyed viscose rayon the spinning machine 10 isadditionally equipped with an individual or multifunctional system formass dyeing 10-1 (FIG. 2). In order for such production to be realized,a preliminarily prepared pigment suspension, made of one or a couple ofpigments, for one production cycle is transferred and stored incontainer 30 (FIG. 2).

By means of pump 31 the required amount of the suspension is dosed intothe viscose, so the viscose and the pigments are mixed and homogenizedin unit 32 (FIG. 2), and as a result the pigment particles are uniformlydistributed throughout the entire volume of the already colouredsolution. The dyed and homogenized cellulose solution is then fed into aviscose pipe line 38 (FIG. 2) of the spinning machine and passed throughthe spinnerets into the spin bath in the already described mode.

In the demonstrated performance of the invention for the production ofantibacterial viscose rayon by recipe (FIG. 4) the suspension of theantibacterial additive is prepared, i.e. 1.0% in relation to the amountof cellulose to be spun for 24 hours. The calculated quantity ofadditive is scaled and quantitatively transferred in the suspensionpreparation container where the required amount of water and othercomponents of the recipe have already been weighted. The preparedsuspension is transported to the container 30 of the individualinstallation for mass dyeing (FIG. 2), after which the feed of thesuspension to the homogenizer 32 from the suspension dosing pump 31 isset. This important setting is performed when the viscose pipe collector38 is filled with the cellulose solution/viscose/ and deaerated. Furtherfollows the spinning as above-described.

After the viscose is mixed with the suspension, whatever it is, as aresult of the dilution its parameters are modified:

Prior to After mixing with mixing with the suspension the suspensionviscosity Sec. 39.0 30.0 ripening ml. NH₄CL 19.25 17.40 temperature ° C.17.0 19.0

The spinning of the viscose solution—antibacterial component complex isperformed in the same spin bath, used for spinning of the same viscosesolution without such an additive or of the same solution, dyed in mass.

After spinning, the freshly-spun sour antibacterial rayon passes throughthe processing to which rayon is subjected, spun through all thespinning machines, i.e. these operations are performed in accordancewith the approved technological requirements and practice. Thesetreatments include washings with softened water, neutralization withsodium carbonate, desulphoration and again washing with softened water.

The drying and rewinding of the rayon cakes to bobbins with standardweight and size is carried out in the same way and parameters like therest of rayon yarn manufactured in the classical mode. The onlydifference is that the rewinding of the antibacterial rayon is performedon separate rewinding machines in order not to mix it with the rest, andit sent to the quality control immediately, after which each bobbin ofantibacterial rayon is wrapped in sterile packaging.

The quality control inspection is performed in the same way as with thetraditionally manufactured types of viscose rayon.

In FIG. 5b are shown the results from the antibacterial tests ofantibacterial rayon, manufactured using the method according to theinvention, and in FIG. 5a —the methodology used to determineantibacterial activities, which is not subject of the invention.

The introduction of any type of additives to the viscose solutionchanges its parameters and especially its ripening speed. That is why,the introduction of the additive in the viscose immediately before itsspinning, which is the innovative solution of the suggested method, isone of its essential advantages as compared to the ones already known,because the changes in the parameters of the cellulose solution/viscose/happen minutes before its direct spinning, which guarantees its stabletrouble-free spinning, with no need whatever changes to be made in therest of the parameters of the spinning process.

1. Method for the manufacture of antibacterial viscose filament rayonbased on following stages: Treatment of the raw cellulose with aconcentrated solution of sodium hydroxide, resulting in alkali cellulosewhich after that is subjected to destruction to reduce its degree ofpolymerization; reduction of the temperature and dosing of the quantityof alkali cellulose for the production of one batch of viscose;treatment with carbon disulphide until it is transformed into cellulosexanthate which is soluble in diluted solutions of sodium hydroxide,mixing and then filtering for removal of the impurities, deaerating andfiltering again after which the already cleared viscose with 8.8%cellulose and 6.4% sodium hydroxide content and ripeness index 18.5-19.5is fed under pressure to the spinning machines. Wet spinning isperformed by passing the cellulose solution, by means of a dosing pump,through the spinneret holes into the spin bath, where as a result of thechemical reactions the cellulose from the cellulose solution transformsinto rayon filament yarn; next treatment with various solutions forremoval of the residues from the spin bath, resulting from the chemicalreactions during spinning; followed by drying, conditioning, rewindingand quality determination, with the main characteristic thatantibacterial additive for raw white bright antibacterial viscosefilament rayon production is added into ready for spinning viscose,mixed and homogenized with it immediately before its spinning on thespinning machine, after which the rest of the described stages arecarried out.
 2. A method for the manufacture of antibacterial viscosefilament rayon dyed in mass, based on following stages: Treatment of theraw cellulose with a concentrated solution of sodium hydroxide,resulting in alkali cellulose which after that is subjected todestruction to reduce the degree of polymerization; reduction of thetemperature and dosing of the quantity of alkali cellulose for theproduction of one batch of viscose; treatment with carbon disulphideuntil it is transformed into cellulose xanthate which is soluble in adiluted solution of sodium hydroxide, mixing and then filtering forremoval of the impurities, deaerating and filtering again after whichthe already cleared viscose 8.8% cellulose and 6.4% sodium hydroxidecontent and ripeness index 18.5-19.5 is fed under pressure to thespinning machines. Wet spinning is performed by passing the dyed in masscellulose solution, by means of a dosing pump, through the spinneretholes into the spin bath, where as a result of the chemical reactionsthe cellulose from the cellulose solution transforms into dyed in massrayon filament yarn; next treatment with various solutions for removalof the residues from the spin bath, the sodium sulphate and the basicsulphur, resulting from the chemical reactions during spinning; followedby drying, conditioning, rewinding and quality determination, with themain characteristic that antibacterial additive and pigment suspensionas antibacterial dyed complex for antibacterial and dyed in mass viscosefilament rayon production are added together into ready for spinningviscose, mixed and homogenized with it immediately before its spinningon the spinning machine, after which the rest of the above—describedoperations follows.
 3. A method according to claim 1, with the maincharacteristic that the quantity of the antibacterial additive addedInto ready for spinning viscose, mixed and homogenized with itimmediately before its spinning on the spinning machine is from 0.01% to5% in relation to the amount of the cellulose in the viscose solution,respectively in ready made antibacterial rayon filament yarn
 4. A methodaccording to claim 1 with the main characteristic that as antibacterialadditive ZINC PYRITHIONE is used.
 5. A method according to claim 1, withthe main characteristic that when antibacterial additive Zinc Pyrithioneis added into ready for spinning viscose, mixed and homogenized with itimmediately before its spinning on the spinning machine, its amount isbetween 0.5 and 3.5% in relation to the cellulose content in the viscosesolution.
 6. Antibacterial viscose filament rayon products row whitebright and dyed in mass obtained using the method according to claim 1.7. Method for the manufacture of antibacterial artificial cellulosefibers with the main characteristic that as antibacterial additive ZINCPYRITHIONE could be used.